Bara Fm
Type Locality and Naming
Kanikot Gr – middle formation. Holotype section: Bara Nai, northern Laki Range. Author: Ahmad and Ghani (written communication-1971, as in Shah, 2009). Reference section: None.
Synonym: Lower Ranikot sandstone
Lithology and Thickness
Coal and Sandstone. Contains one of the biggest lignite deposits in the world. In the type section, it dominantly consists of sandstone with lesser shale and minor volcanic debris. The sandstone is varicolored, fine to coarse grained, soft and crumbly. Massive looking beds ranging in thickness from a few centimeters to 3 m are common. It is calcareous, ferruginous, ripple marked and cross-stratified. The interbedded shale has dark shades of color similar to that of sandstone and is soft, earthy and gypsiferous; shales at places contain coal seams, while further east in subsurface at the Thar Coalfield some volcanic debris, weathering greenish grey to black, has been reported from the lower part of the formation.
Thickness: 60-600 m (based on surface exposures). It is 450 m at the type section, 600 m at Ranikot section, 140 m at Rakhi Nallah (Gorge Beds of Eames, 1952) and 60 m in northern part of eastern Sulaiman Range (Williams, 1959). Please see explanation under Ranikot Group and Khadro Fm above for the erroneous thickness reporting in oil wells, including offshore. The large Thar Coal deposits are found in this formation.
Relationships and Distribution
Lower contact
Conformably underlain by Khadro Fm, and by the basement in Thar area.
Upper contact
Regional extent
The formation is widely distributed in the Kirthar Province and the Axial Belt. Towards eastern Sulaiman Range in the north it has earlier been reported from one locality (Rakhi Nallah) where 'Gorge Beds' (Eames, 1952) have been formalized as Bara Fm, farther north relatively thin development of the formation is reported by Williams (1959). The lower part of the Dunghan Fm is also stratigraphically equivalent to Bara Fm in the southern part of Indus Basin.
GeoJSON
Fossils
No fossils have been found, except for some oysters, reptile remains and carbonized leaf impressions. However, Vredenburg (1928) recognized Ostraea talpur --The basis of assigning Thanetian age to these beds.
Age
Depositional setting
The formation appears to be of fluviatile origin
Additional Information
EMW: Thar Coalfield, one of the biggest lignite deposits in the world, spread over an area of 9,100 sq. km., occupies the southeastern corner of Pakistan. The cumulative thickness of coal beds varies between 7 and 36 m. The overburden thickness varies from 114 to 245 m above the first coal seam, and the sand dunes above the average ground level increase the depth by another 30 m. The reserves are estimated to be more than 175 billion tonnes. The coal beds are generally encountered in the upper half of the formation. China clay layer invariably forms the roof, and also floor of the rock (in contact with the basement).